Tungsten carbide nanofibers prepared by electrospinning with high electrocatalytic activity for oxygen reduction

Tungsten carbide (WC) nanofibers with ultrafine diameters were synthesized by carbonizing the as-spun ammonium metatungstate (AMT) and polyvinyl pyrrolidone (PVP) composite fiber precursors. The morphologies of the WC nanofiber products were closely related to the electrospinning concentrations of AMT and PVP. Raman spectra and high resolution TEM (HR-TEM) testified that the surface of the WC nanofibers was coated by a carbon layer with a thickness of several nanometers, which could be removed to a great degree by NH3 etching at high temperature. Cyclic voltammetry (CV) and rotating disk electrode (RDE) test results showed that the carbon-coated WC nanofibers had good electrocatalytic activities and stabilities during oxygen reduction reaction (ORR), both of which could be further improved by NH3 post-treatment at high temperature. The catalytic roles of the WC nanofiber samples for ORR probably originated from the WC sites, but not excluding some contributions of the surface carbon species.